Download Homeostasis: process of maintaining consistent

Homeostasis: process of maintaining consistent composition of body’
composition of body’s extracellular
s extracellular fluid
• Extracellular fluid (ECF)
– Fluid environment in which the cells live (fluid outside the cells)
– Major components: • Plasma
• interstitial fluid
– Minor ECF components
– Lymph, transcellular fluid,cerebrospinal fluid, Intraocular fluid, synovial fluid, pericardial, intrapleural, and peritoneal fluids,digestive juices
• Intracellular fluid (ICF)
– Fluid contained within all body cells
Fig. 1-5, p. 7
1 = capillary membrane separating plasma from interstitial fluid
Barriers Separating Body‐Fluid Compartments
• Barrier between plasma and interstitial fluid
– Blood vessel walls
• Barrier between ECF and ICF
– Cellular plasma membranes
2
2 = cell membrane separating ICF and ECF
3 = interstitial fluid
1
Blood= plasma + cells
4 = intracellular fluid
5
5 = plasma, which is a part of blood; ECF trapped in capillary vessels
3
4
Plasma
Barriers Separating Body‐Fluid Compartments
HCO3–
150
Capillary wall
Na+
HCO3–
Plasma membrane
• Presence of cell proteins in ICF that cannot permeate the cell membrane to leave the cells
• Unequal distribution of Na+ and K+ and their attendant ions
• Overall electric (charge) balance between intracellular and extracellular fluid
• Overall osmotic balance between intracellular and extracellular fluid
200
Milliequivalents per liter of H2O
– Major differences between Extracellular
Interstitial Fluid and Intracellular Fluid (ICF)
Intracellular
fluid
(skeletal muscle)
Interstitial
fluid
PO43–
K+
100
Na+
Cl–
Na+
Cl–
50
Protein
anions
0
Protein
K+ anions
Other Other
Cations Anions
Other
K+
Other
Cations Anions
Other
Cations Anions
Fig. 14-2, p. 419
What is the expected volume of each compartment in a person weighing
weighing
XXX pounds who is normally hydrated?
 Total Body Water (liters) = 60% of body weight kg
► Convert pounds to kilograms,
► multiply by .6 Liters/kg body weight to estimate Liters of Total
Body Water
 ICF = 2/3 of TBW
ECF = 1/3 of TBW
› Interstitial fluid = 75 – 80% of ECF
Use 75%
› Plasma = 20-25% of ECF
Use 25%
40% of body
weight is
intracellular fluid
20% of body
weight is
extracellular fluid
(Your body weight / 2) - 10% of answer = your weight in kg
160 lbs / 2 = 80
actual conversion160/2.2= 72.72
80 – (10% of 80) ~ 72 kg
 The primary extracellular fluid (ECF) cation is sodium
 The primary intracellular fluid (ICF) cation is potassium.
 This difference is maintained by the Na+/K+ ATPase , which transport three Na+
160/2.2026 = 72.64
molecules out of the cell in exchange for two K+ molecules transported into the cell.
 A balance of positive and negative charges is maintained in each
compartment, but by different ions.
Assume 1 kg weight = 1 liter fluid
60% of
72kg, in
liters
72 kg
28.8 43.2 10.8 14.4 3.6 Homeostasis
Maintain
• Factors homeostatically regulated include
Homeostasis
(consistency of ECF)
Body
systems
Which is essential for
function (1- 6, + specialized) of
that make up
Cells
Cell activity upsets (disorders) and restores (orders) ECF
Fig. 1-6, p. 7
–
–
–
–
–
–
–
Concentration of nutrient molecules
Concentration of O2 and CO2
Concentration of waste products
pH (concentration of free H+ or protons)
Concentration of water, salt, and other electrolytes
Blood volume and blood pressure
Body Temperature
Body System Contributions to Homeostasis
• Circulatory system
– Carries materials from one part of the body to another
• Digestive system
– Breaks down dietary food into smaller molecules that can be distributed to body cells
– Transfers water and electrolytes from external environment to internal environment
– Eliminates undigested food residues to external environment in the feces
Body System Contributions to Homeostasis
• Skeletal system
– Provides support and protection for soft tissues and organs
– Serves as storage reservoir for calcium
– Along with muscular system enables movement of body and its parts
– Bone marrow is ultimate source of blood cells
• Muscular system
– Moves the bones
Body System Contributions to Homeostasis
• Respiratory system
– Gets O2 from and eliminates CO2 to the external environment
– Important in maintenance of proper pH of internal environment
• Urinary system
– Removes excess water, salt, acid, and other electrolytes from plasma and eliminates them in urine; balances fluid and electrolytes
Body System Contributions to Homeostasis
• Integumentary system
– Serves as outer protective barrier
– Important in regulating body temperature
• Immune system – Defends against foreign invaders and against body cells that have become cancerous
– Paves way for repairing or replacing injured or worn‐out cells
Body System Contributions to Homeostasis
Body System Contributions to Homeostasis
• Nervous system
– Controls and coordinates bodily activities that require rapid responses
– Detects and initiates reactions to changes in external environment
• Endocrine system
• Reproductive system
– Not essential for homeostasis (not essential for survival of individual)
– Is essential for perpetuating the species
– Secreting glands of endocrine regulate activities that require duration rather than speed
– Controls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte composition
Homeostatic Control Systems
• In order to maintain homeostasis, control system must be able to
– Detect deviations from normal in the internal environment that need to be held within narrow limits
– Integrate this information with other relevant information
– Make appropriate adjustments in order to restore factor to its desired value
Fig. 1-7, p. 12